Question
In Spider Man: Far From Home, Mysterio talks to Peter about the multiverse. Although it's a lie, he clearly mentions the universe 616, which is the main marvel universe (anyone who reads the comics or watched the animated TV series knows this).
But we (or those in the cinematic universe) only were presented to multiverse names in the new Dr. Strange in The Multiverse of Madness.
Mysterio could've guessed they live in a multiverse, but how could he know that they're living in 616?
He does not have superpowers or an intelligence like Tony, Reed or Banner.
Answer
Out of universe, this is pretty clearly an example of something that was intended to be an Easter egg to the comic lore, before that aspect later became incorporated into the actual MCU canon. There is no chance that when Far From Home came out, the writers intended Beck's comment to be a factual statement about the nature of multiverses.
That said, having seen Multiverse of Madness: why couldn't he have dreamed it? Dreams are revealed to be visions into alternate universes that even ordinary people have. For all we know, in the 838 universe, the technically brilliant Beck works closely with the Illuminati and is aware of universe 616, which the 616-Beck subconsciously works into his act after a dream.
Answered By - TenthJustice
